In small shops and especially for light duct work, it is desirable to utilize a hand power tool that is useful for closing sheet metal joints, such as those commonly known in the trade as "pittsburgh locks". In the past there have been many proposals, and several commerical structures, for effecting such results, such as shown in U.S. Pat. Nos. 3,195,492 and 3,487,669. While such structures can accomplish their intended results, despite efforts to the contrary, they often result in damage to the surface of the sheet metal flanges being deformed, and can be especially damaging to painted surfaces. Also, such structures may be difficult to operate, especially where the metal is anything besides the lightest gauge, and where unskilled laborers are expected to operate the structures.
According to the present invention, a metal-working hand tool is provided for closing pittsburgh locks and the like that is able to effectively fold over sheet metal flanges of a wide variety of gauges normally encountered in the field, yet can effect such results without any damage at all to the metal flange surfaces being folded over, even if the surfaces are painted. The hand tool according to the invention is utilizable in a simplified method of effecting the flange deformation that is fail-safe in use, and makes the structure properly operable by even unskilled laborers.
According to the present invention, a metal-working hand tool is provided for folding over sheet metal flanges that includes a body adapted to rotate about a first axis, means for attaching the body to a power source for rotating the body about the first axis, and a guide component extending outwardly from one end of the body generally along the first axis. A plurality of hardened metal roller means are mounted to the body for free rotation about second axes, fixed with respect to the body, so that the roller means will impact upon and roll with respect to a sheet metal flange or the like. While such action is very sure in effecting flange deformation, the relative rolling that takes place between the roller means and the work prevents damage to the surface of the work.
The roller means mounting means according to the invention, preferably comprises a shaft for each roller means disposed so that each second axis makes a positive angle .alpha. between 0.degree. and 90.degree. with respect to the first axis, the angle .alpha. preferably being about 35.degree. to 55.degree.. The shafts are disposed along lines converging at the interface between the guide component and the body, and each shaft may include a dowel pin that is releasably attached to the body. The roller means preferably each comprise a tapered roller having flattened end portions received within a cavity defined in the body and having a peripheral portion extending exteriorly of the body, preferably three rollers being provided disposed at the apices of an equilateral triangle, around the circumference of the body. The attaching means may comprise means defining a screw-threaded bore concentric with the first axis in the body and opposite the guide component, and the guide component may comprise a guide pin having a head portion abutting an axial termination of the screw-threaded bore.
Utilizing the hand tool according to the present invention, a simplified method of deforming an upturned sheet metal elongated flange of a metal joint to close the joint is provided. The method includes the steps of disposing the metal joint so that the metal flange extends generally vertically, effecting energization of the tool to rotate the body, disposing the guide components so that it is in a direction generally parallel to the metal flange, and moving the guide component into contact with a side of the joint (for guiding movement) while moving the tool generally horizontally along the direction of elongation of the flange, to deform it so that it extends generally horizontally. Practicing such a method, it is possible for even unskilled laborers to acurately and quickly effect joint closing without damage to the work.
It is the primary object of the present invention to provide an improved hand tool and method for folding over sheet metal flanges. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.